Heat pumps are now the preferred option for both new builds and existing homes undergoing an energy retrofit. The units, which operate like a fridge in reverse, run off electricity, which is increasingly generated by renewables, doing away with the need for polluting fossil fuels.
By keeping the house at a constant, comfortable heat, they also do way with the constant round of heat blasts that comes from life with a boiler and thermostat.
“The advantage of the heat pump is that the home is designed around the heat pump, and not the other way around. That means having better levels of airtightness because you have better insulation, better windows and doors, so the home doesn’t need as much heat,” says Shane Toye, consultant sales engineer at Mitsubishi Electric Ireland, one of the biggest providers of electric heat pumps (stand N80 at the PTSB Ideal Home Show).
It’s why “comfort” is the sentiment most expressed in Mitsubishi’s customer feedback, he adds.
READ MORE
Both for new builds and deep retrofits, the combination of a heat pump and a mechanical ventilation with heat recovery system (MVHR), working in tandem, is the optimum solution.
“Older properties would have had natural leakage, with air circulating around the house. But whenever you close the house in and make it airtight, you have to introduce that fresh air. The house must have it to breathe,” says Toye.
Heat recovery and mechanical ventilation systems are highly efficient and ensure fresh air is constantly drawn in from the outside and dispersed to bedrooms and living areas.
At the same time, they extract damp, humid air from wet areas, such as bathrooms and kitchens. This air is then passed through a heat-recovery unit, which is typically located in your attic or hot press, where the heat is extracted from it for reuse, and the rest of the “bad” air dumped outside, while clean fresh air is drawn back in. “So you’re always moving fresh air through the house,” says Toye.
Obviously it’s easier with a new build but both heat pumps and ventilation systems can be installed in a retrofit situation; it just means more work. “To do it properly, you’re generally looking at a fairly deep retrofit – in many cases, close to a full gut,” says Dan Fagan, managing director of Ashmore Building (stand L83 at the PTSB Ideal Home Show).
“From a heat-pump point of view, the fabric of the house is the key thing. For a heat pump to be worth the investment and run efficiently, you need good insulation levels throughout and improved airtightness. If that isn’t addressed, you’ll have too much heat loss, the system will end up working harder, and running costs can climb. So it’s not just about putting in a heat pump – it’s about getting the house to a standard where it can actually perform properly.”
Ventilation can also be retrofitted but is more invasive again. “A full system involves ductwork through floors, ceilings and sometimes walls, particularly in two-storey homes, so the house usually needs to be opened up quite a bit. Because of that, it tends to make most sense where a bigger renovation is already happening,” Fagan explains.
There are simpler options in less extensive retrofits. “Demand-controlled ventilation, combined with humidity-sensitive wall vents, can be a more practical way of improving air quality without the same level of disruption,” he points out.
“A heat pump will work without a dedicated ventilation system, but in best practice the two go hand in hand. Once you improve airtightness, you need a controlled way to bring fresh air in and remove moisture. Without that, you can run into issues like poor air quality or condensation. So while you don’t always need a full ventilation system, you do need to have some form of ventilation strategy in place.”
It’s about health as much as heat.
“It’s actually about making sure you are removing indoor air pollutants, such as radon in houses, or particulates that build up from cooking,” explains Brian McIntyre, programme manager, high performance building technologies, at the Sustainable Energy Authority of Ireland (SEAI).
“Let’s be honest, no one has a perfectly clean oven, and burning particles can release particulate matter into the air inside the house that we don’t necessarily always get rid of. We often don’t leave the hood on over the hob for long enough after we’ve cooked, for example. Then we have other particulates, such as formaldehyde from new furniture and furnishings, and all the indoor air pollutants that can build up in a house if we don’t ventilate it properly.”
In rooms with high levels of humidity, such as bathrooms, the result can be mould. “Humidity is something dust mites love too,” he points out. “Because they can’t ingest water, they have to absorb it from the air, so they just love if you don’t have enough ventilation; they thrive on it.”
Humidity is not only found in wet areas such as kitchens and bathrooms – we generate moisture as we breathe overnight, which is why bedrooms are a breeding ground for dust mites too, he adds.
On the other hand, says McIntyre, “a properly ventilated house basically kills off dust mites.”
For more information on the show and to register for free tickets, visit idealhome.ie.
